1. Field of the Invention
The present invention relates generally to a weft yarn sensor for sensing whether a weft yarn is satisfactorily inserted or not and particularly to a weft yarn sensor of this type which is formed of a sensor body having an aperture opening externally of the sensor body and two contacts located in the aperture and engaged with each other by an elastic force, the sensor body having a first position for passing the inserted weft yarn through the aperture during insertion and a second position for causing the inserted weft yarn to be taken out from the aperture by having the weft yarn disengaged the contacts, and which senses the presence and absence of the inserted weft yarn from the contacts being disengaged and remaining engaged, without being affected by sticking of a fibrous flue to the sensor, when the sensor body is moved into the second position.
2. Description of the Prior Art
As is well known in the art, in an air jet shuttleless weaving loom of a type which a weft yarn is inserted by entraining the weft yarn into a jet of air, as an expedient for sensing whether the weft yarn has been satisfactorily inserted or not, a weft yarn sensor has been employed which includes a light beam generating section and a light beam receiving section both located on the opposite side of the warp yarn sheets to the air injection nozzle side thereof and confronting each other so that the course of the inserted weft yarn is interposed between the generating and receiving sections. According to this prior art, the presence and absence of the inserted weft yarn are sensed by sensing an electric output of the receiving section varied in accordance with variations in the quantity of light beam to the receiving section due to the presence and absence of intersection with the inserted weft yarn.
However, when the weaving loom weaves short fibres such as cottom yarh which is easy to produce a fly fluff, since the fly fluff sticks to the light beam generating and/or receiving section to intercept the light beam incident to the receiving section, the conventional weft yarn sensor has generated a signal indicating the presence of the weft yarn notwithstanding that no weft yarn has been inserted.